Audiovisual equipment and casing thereof and method of producing the same

Abstract: A casing for an audiovisual equipment presents an outer appearance giving the impression of integrating a hole area formed of a plurality of sound transmitting fine holes with the casing, thereby making the hole area unnoticeable. This allows a viewer to easily concentrate on the screen by eliminating anything noticeable from the area surrounding the screen, and also gives the outside of the casing a luxurious appearance. In order to make the hole area unnoticeable, maintain good volume and quality of sound from the speaker, and arrange the diameter ød mm of the tapered fine holes to be practically the smallest, the relationship between the diameter ød mm and the thickness T mm of the casing must be expressed by the following formula: (1/6) x T mm ≦ ød mm ≦ 0.5 mm. When the fine holes are formed to be straight, the relationship between the diameter øds mm and the thickness tmm of the casing must be expressed by the following formula: (1/5) x t mm ≦ øds mm ≦ 0.5 mm.

Description: The present invention relates to a casing (cabinet) for an audiovisual apparatus, which casing has holes through which sound is transmitted to the exterior of the apparatus from a built-in speaker, and also to a method of producing the same. Nowadays, in television receivers having built-in speakers, many attempts are made to make the area comprising numerous sound transmitting holes (hereinafter simply referred to as "the hole area") less noticeable in order to present an attractive outer appearance and which gives the impression of integrating the hole area with the casing. One object of such attempts is to allow a viewer to easily concentrate on the screen by eliminating anything noticeable from the area surrounding the screen and another object is to give the outside of the casing a luxurious appearance. In addition to these objects, another object of the present invention is to eliminate a separation process for recycling audiovisual apparatuses. Fig 9 shows one example of conventional hole areas which are constructed as follows. A speaker net 40 having good air permeability adheres to a punched sheet 41 having numerous holes 42, each with a diameter greater than 0.5mm. The resultant member is attached to a plurality of sound transmitting holes 43, each having a diameter of approximately 3mm, which holes are arranged on the front or side surface of a casing (cabinet) 50 of a television receiver. However, the above construction presents the following problems. Since the speaker net 40 cannot be formed of the same resin material as the casing, but must be formed of a fibre material or a metal gauze, it must be separated when the audiovisual apparatus is recycled. Moreover, the fibrous speaker net is expensive, and also, a considerable amount of time is required for attaching the speaker net to the punched sheet and the casing. In a small audiovisual apparatus which is directly provided with numerous sound transmitting holes in a cabinet thereof, the diameter of the holes is large relative to the thickness of the casing. For example, the holes have a diameter of approximately 1mm to 2mm relative to the casing having a thickness from 0.5mm to 1.6mm. Thus, the sound transmitting holes forming the hole area are obviously noticeable and conspicuous in terms of the outer appearance of the apparatus. Even in a large casing, such as a television receiver, no attempts have been made to decrease the diameter of the holes until they become substantially unnoticeable. One of the reasons for this is given below. According to conventional techniques, it is believed that the diameter D/mm of the mass-producible holes must be the same or larger than the thickness T/mm of the casing. Consequently, if it is desired that the diameter of a plurality of holes forming the hole area be decreased until they become unnoticeable in terms of the outer appearance of the apparatus, the thickness of the casing must be decreased in accordance with the diameter of the holes, thus failing to ensure the physical strength of the casing. Another reason is described as follows. It will be readily understood that it is technically difficult to arrange such numerous unnoticeable fine holes so as to form a hole area, and thus only very low productivity can be achieved. US-A-4 919 227 discloses a casing for an audio speaker having a thickness greater than the diameter of sound transmitting holes. The sound transmitting holes are located in a grill member which is attached to the casing over a speaker diaphragm. The grill member has two sets of misaligned sound transmitting holes which allow sound to emanate from the speaker but which prevent objects being pushed through the grill member to damage the diaphragm. G8-A-2 249 454 discloses a speaker front comprising a perforated sheet having a plain gauze fabric bonded to the front surface thereof and an adhesive layer applied to a portion of the back surface thereof. The gauze fabric covers the holes (perforations) in the sheet rendering said holes unnoticeable. US-A-4 395 079 discloses a cabinet (casing) having a loud speaker window. The window has a mesh screen comprising a plurality of latitudinally extending and longitudinally extending plastic threads moulded fogether to give a woven metal mesh appearance. An object of the present invention is to provide a casing (cabinet) which presents a good appearance without requiring a conventionally-used speaker net and punched sheet by forming a hole area comprising a plurality of unnoticeable fine sound transmitting holes. The present invention provides a casing for an audiovisual apparatus, said casing including a sound transmitting hole area in at least one surface of the casing, the sound transmitting hole area having a plurality of holes formed by an injection moulding process and said casing having a thickness (T) over the transmitting hole area of 0.5mm or more, wherein the width (d) in millimetres of any one of said holes 6D) adjacent to the exterior of the casing obeys the relationship: 1/6T ≤ d ≤ 0.5 The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments with reference to the accompanying drawings, of which:- Fig. 1 is a sectional view of an essential portion of a television receiver according to a first embodiment of the present invention; Fig. 2 is a front view of an essential portion of a television receiver according to the first embodiment of the present invention; Fig. 3 is an enlarged sectional view of an essential portion of fine holes according to the first embodiment of the present invention; Fig. 4 is an enlarged sectional view of an essential portion of another type of fine holes according to the first embodiment of the present invention; Fig. 5 is a front view of an essential portion showing one arrangement for the fine holes according to the first embodiment of the present invention; Fig. 6 is a front view of an essential portion showing another arrangement for the fine holes according to the first embodiment of the present invention; Fig. 7 is an enlarged sectional view of an essential portion of a hole area and fine holes according to a second embodiment of the present invention; Fig. 8 is an enlarged sectional view of an essential portion of another type of hole area and fine holes according to the second embodiment of the present invention; Fig. 9 is a sectional view of an essential portion of a conventional television receiver. First Embodiment Figs. 1 - 6 show a television receiver 100A and an area comprising holes through which sound is transmitted according to a first embodiment of the present invention. The television receiver 100A includes an electronic circuit 20 and also accommodates a CRT (cathode-ray tube) 4, a speaker body 2 and a speaker box 3 within a casing 1A. The casing 1 A can be produced by injection-molding a resin material, for example, polystyrene (PS). The casing 1A is provided with a sound transmitting hole area comprising a plurality of sound transmitting holes 6A on at least one of its surfaces, for example, the front surface (the surface facing viewers) and a side surface as shown in Figs. 1 and 2. The sound transmitting fine holes 6A have a diameter of less than the thickness of the casing, for example, 1.6mm. As illustrated in Fig. 3, the sound transmitting fine holes 6A are formed to be tapered such that they have a greater diameter D adjacent to the interior of the casing 1A and a smaller diameter d adjacent to the exterior of the casing 1A, and are produced by one-shot molding integrally with the casing 1A according to the injection molding method as stated above. Many patterns are available to arrange the plurality of sound transmitting fine holes 6A. For example, they may be arranged in a plurality of rows and columns as shown in Fig. 5, or may be arranged concentrically as illustrated in Fig. 6. In this embodiment, the inventors examined the diameter of the sound transmitting fine holes 6A and the pitch arrangement of the holes (hereinafter simply referred to as "the pitch") when the hole area is formed by arranging the sound transmitting holes 6A in a plurality of rows and columns as shown in Fig. 5. The diameter of the sound transmitting holes 6A was arranged to be 0.3mm, because as a result of our examination, we found that the hole area for commonly-used dark-colored casings was not noticeable if the diameter of the holes was 0.5 mm or less. A casing having a plurality of such sound transmitting fine holes, approximately 40,000 for a television receiver, can be mass-produced. This is because the following production technique is available. An injection mold having a plurality of elongated pins is produced with high precision, and then, resin molding is performed at low pressure. The smaller the diameter of the sound transmitting holes advantageously makes the hole area less noticeable. However, the smaller the diameter, the less effective such an advantage becomes. That is, the effect gained by making the area even less noticeable is very little. Also, if the diameter of the sound transmitting holes is made smaller, more holes are required in order to maintain good volume and quality of sound from the speaker. That is, it is necessary to have more numerous narrower pins within the injection mold. This accordingly requires an injection mold with higher precision and a more advanced production technique, thus inevitably resulting in an increase in cost. Therefore, the smallest practical diameter of the sound transmitting holes must be determined so as to balance the advantages gained by making the diameter small and the disadvantages caused by the increased cost required to do so. The diameter d mm of the sound transmitting holes 6A must be the smallest practical size but to such a degree that the hole area is not noticeable and that good volume and quality of sound from the speaker can be maintained. As a result of our examination, the relationship between the thickness T/mm of the casing 1 A and the diameter d mm of the holes may be expressed as follows: (1/6) × T/mm ≤ d/mm ≤ 0.5 In this embodiment, the diameter of the sound transmitting holes and the pitch therebetween were determined as follows. As shown in Fig. 3 and 5 the diameter d of the holes adjacent to the exterior of the casing 1 A was 0.3mm; the diameter D of the holes adjacent to the interior of the casing 1 A was 0.6mm; the pitch of the holes in the horizontal direction (hereinafter simply referred to as "the horizontal pitch") was 1.6mm; the pitch of the holes in the vertical direction (hereinafter simply referred to as "the vertical pitch") was 0.47mm. If the sound transmitting holes are constructed of straight holes 6B shown in Fig. 4 instead of tapered holes, the relationship between the thickness t mm of the casing 1A and the diameter ds/mm of the sound transmitting holes 6B may be expressed as follows: (1/5) × t/mm ≤ ds/mm ≤ 0.5 1/6 in the previous expression is replaced by 1/5 in this expression because pins within an injection mold for straight holes must be smaller than the pins for making tapered holes. In this embodiment, when t was 1.6mm, ds was arranged to be 0.36mm. The horizontal and vertical pitches were arranged as the same or slightly smaller than those of the tapered holes. The sound transmitting holes 6B are integrally produced by one-shot molding with the casing according to the injection molding method in a manner similar to those of tapered holes. It is more difficult to release the product from the mold when the fine holes 6B are formed to be straight than when the fine holes 6A are formed to be tapered, and the strength of the pins within the mold for forming the fine holes 6B is lowered. Thus, the diameter of the sound transmitting holes was arranged to be 0.36 mm. The shape of the sound transmitting holes is not limited to a circle, but may be a polygon having a diagonal line smaller than the thickness of the casing, or an oval or an ellipse having a maximum chord smaller than the thickness of the casing. Also, the position on which the sound transmitting holes are arranged is not limited to the front and side surfaces of the casing, but may be placed on a desired position, for example, on the top or bottom surfaces, or curved surfaces at the corner of the casing. In the first embodiment of the present invention, since a speaker net and a punching sheet are not used, an adhering operation can be omitted and the hole area 5 can be produced simultaneously with molding the casing 1A according to the one-shot molding method, thus resulting in higher productivity than the conventional construction. Second Embodiment The second embodiment differs from the first embodiment in the method of molding the hole area arranged on the surface of the casing. More specifically, the casing is primarily molded according to the injection molding method and then, the mold is moved or turned so as to secondarily mold the hole area. This is called a double-shot molding method. Since the hole area is secondarily molded, the mold can be constructed simply, and also, the type of material forming the hole area produced by the secondarily molding can be varied. Figs. 7 and 8 are sectional views of essential portions of the casing and the hole area formed by double-shot molding. Referring to Fig. 7, the thickness of the casing 1C formed by the primary molding is equal to that of the hole area 5C formed by the secondary molding, and the sound transmitting fine holes 6C are tapered. The thickness of the casing, the diameter and the vertical and horizontal pitches of the holes are the same as those in the first embodiment. Further, projected and recessed portions 70 are formed in the central area along the thickness of the casing in order to avoid the separation of the casing 1C and the hole area 5C. Referring to Fig. 8, the thickness of the casing 1 D formed by the primary molding differs from that of the hole area 5D formed by the secondary molding, and the sound transmitting fine holes 6D are made straight More specifically, the thickness of the hole area 5D is arranged to be one half or less than that of the casing 1 D, thereby simplifying the formation of the holes 6D. The thickness of the casing, the diameter and the vertical and horizontal pitches of the holes are the same as those in the first embodiment. In the second embodiment shown in Fig. 8, the thickness of the hole area 5D was arranged to be 0.6mm; the diameter of the straight holes was arranged to be 0.3 mm; the horizontal and vertical pitches of the holes were arranged to be 1.6 mm and 0.47 mm, respectively. In the second embodiment, the type of material forming the casings 1C and 1 D and that of the hole areas 5C and 5D can be varied according to necessity.

Claims: A casing (1A;1B;1C;1D;1E) for an audiovisual apparatus (100A;100E), said casing (1A;1B;1C;1D;1E) including a sound transmitting hole area (5;5C;5D) in at least one surface of the casing, the sound transmitting hole area having a plurality of holes (6A;6B;6C;6D) formed by an injection moulding process and , said casing having a thickness T over the transmitting hole area of 0.5mm or more, wherein the width d in millimetres of any one of said holes (6A;6B;6C;6D) adjacent to the exterior of the casing (1A;1B;1C;1D;1E) obeys the relationship: T/6 ≤ d ≤ 0.5 mm A casing as claimed in claim 1, wherein the thickness of said casing (1A;1B;1C;1D;1E) over the transmitting hole area is 1.6mm or less. A casing as claimed in claim 1 or claim 2, wherein the width d of any one of said holes (6A;6B;6C;6d) adjacent to the exterior of the casing (1A;1B;1C;1D;1E) is in the range of 0.3 to 0.5mm. A casing as claimed in any preceding claim, wherein each of the holes has a constant width along its length. A casing as claimed in any one of claims 1 to 3, wherein each of the holes is tapered along its length. A casing as claimed in claim 5, wherein each of the holes is tapered along its length and has its smallest width adjacent to the exterior of the casing. A casing as claimed in any preceding claim, wherein each of the holes has a circular cross-section. An audiovisual apparatus (100A;100E) including a casing (1A;1B;1C;1D;1E) as claimed in any preceding claim. A method of producing a casing (1A;1B;1C;1D;1E) for an audiovisual apparatus (100A;100E) comprising; forming a casing having a sound transmitting hole area (5;5C;5d) in at least one of its surfaces, the sound transmitting hole area being formed with a plurality of holes (6A:6B:6C:6D) by an injection moulding process, and said casing being formed to have a thickness T of 0.5mm or more over the transmitting hole area, wherein the casing is formed such that the width d in millimetres of any one of said holes adjacent to an exterior of the casing obeys the relationship: T/6≤d≤0.5mm A method as claimed in claim 9, wherein the casing (1A;1B;1C;1D;1E) is formed to have a thickness over the transmitting hole area of 1.6mm or less. A method as claimed in claim 9 or claim 10, wherein the casing is formed such that the width d of any one of said holes adjacent to the exterior of the casing is in the range of 0.3 to 0.5mm. A method as claimed in any one of claims 9 to 11, wherein the casing is formed such that each of the holes has a constant width along its length. A method as claimed in any one of claims 9 to 11, wherein the casing is formed such that each of the holes is tapered along its length. A method as claimed in claim 13, wherein the casing is formed such that each of the holes is tapered along its length and has its smallest width adjacent to the exterior of the casing. A method as claimed in any one of claims 9 to 14, wherein the casing is formed such that each of the holes has a circular cross-section. A method as claimed in any one of claims 9 to 15, wherein the casing (1A;1B;1C;1D;1E) is formed by an injection moulding process. A method as claimed in claim 16, wherein the transmitting hole area (5) of the casing (1A) including the plurality of holes (6a) is simultaneously formed with the casing by a single injection moulding process. A method as claimed in claim 17, wherein the plurality of holes (6A) in the transmitting hole area (5) of the casing (1A) are formed by a plurality of pins comprising part of the mould. A method as claimed in claim 16, wherein the transmitting hole area (5C;5d) of the casing (1C;1D) including the plurality of holes (6C;6D) is integrally formed with the casing (1C;1D) by a secondary injection moulding process subsequent to a primary injection moulding process for forming the casing (1C;1D). A method as claimed in claim 19, wherein the material used for forming the casing (1C;1D) in the primary injection moulding process is different from the material used for forming the transmitting hole area (5C;5D) in the secondary injection moulding process. An audiovisual apparatus including a casing formed by a method as claimed in any one of claims 9 to 20.

Inventors: SHIKATA NAOHIRO, SHIMIZU KAORU, SHIOTA TOMIO, SHIKATA, NAOHIRO, SHIMIZU, KAORU, SHIOTA, TOMIO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: H04N5
IPC codes: H04R5, H04N5, H05K5, H04R1